1. Field of the Invention
The invention relates to the dismantling from a substrate of a microelectronic component which is both attached to a substrate by its base and soldered by connecting pieces to conductors on the said substrate.
2. Description of the Prior Art
The ever-increasing miniaturisation of electronic systems, principally in computers, has led recently to a technology in which the active and/or passive elements are produced in the form of non-coated integrated circuits directly mounted on substrates of ceramic forming multi-layer printed circuits. The upper layer of the substrate comprises conductors which are at least partially covered by a layer of solder (principally an indium-lead alloy), some of which are fitted to or end in studs which are disposed along a given perimeter within which an electric modular component (an integrated circuit including a certain number of transistors, diodes, resistors and possibly capacitors) is attached by its base on the substrate. The modular electronic component further comprises a number of connecting pieces which protrude laterally along its edge and which are attached to the studs. Mounting of these modular components is therefore made both by attaching the base on the substrate and by soldering the end of the connecting pieces to the corresponding studs of the substrate. The soldering is effected in a single step by the fusion of an indium-lead alloy previously placed on the substrate and principally on the studs. This technique has numerous advantages both insofar as concerns the degree of miniaturisation attained and the reliability of the circuits. However, it can happen that one of the modular components is found to be defective on checking, or again that a modification in the concept of the apparatus necessitates the replacement of one or more modular components which have already been mounted on a certain number of substrates, for example in the context of the contruction of a prototype of preproduction.
The replacement of such modular components poses a number of problems. First of all, if the modular component is not defective it is useful to be able to retrieve it intact so as to possibly reuse it in another circuit. Since the connecting pieces of this modular component are extremely fragile, a wrong move in the course of dismantling it can very easily cause the breaking off of one or more of these connecting pieces. Since the modular component is both attached on the substrate and soldered to the conductors on the substrate by all the connecting pieces, it is therefore necessary to be able to melt the adhesive and all the soldered connections before removing the modular component. This operation is very difficult to carry out manually. Secondly, it is especially important to preserve the substrate which should definitely be reused. In particular, it is important not to damage the layer of solder on the conductors carried by the external surface of the substrate and notably the parts of this layer which are on the studs, since the solder at this point must then be reused for the electric connection of the replacement modular component. The invention seeks to provide a satisfactory solution to all these problems.